Small molecules are believed to move directly between the cytoplasms of adjacent cells by means of gap junctions, cell-cell specializations which are distributed widely in multicellular organisms. A model intercellular communication has been developed as a result of these observations. However, no specific probe is available for experimentally evaluating this model and addressing other questions of junctional organization, formation and function. This proposal focuses on the production of antibodies to the proteins of gap junctions, the characterization of these antibodies and the development of methods for applying these probes to the above questions. The proposal takes advantage of recent advances in our understanding of junctional proteins, relevant isolation schemes and immunological methods. We will analyze gap junction fractions isolated without proteases from rat liver to determine whether the 26 kilodalton proteins are authentic junctional components. We will also devise methods for studying the specific binding of immunoglobulins to intact junctional fractions and junctional proteins separated electrophoretically. If necessary, we will explore a number of possible techniques to determine an effective procedure for the production of immunoglobulins directed against the antigens of rat liver gap junctions. In addition, we will begin to develop monoclonal antibodies to the proteins of gap junctions. Finally, we will determine whether any antisera that bind to rat liver junctional protein will also bind to these proteins in Novikoff hepatoma cells and, if so, whether the antisera have any effect on gap junctions in this culture system.